Dans le présent article, surface de Riemann ou plus simplement surface désignera une variété analytique complexe R, connexe, sans bord et de dimension 1. En terme d'une variable locale, une fonction harmonique h, définie sur R, possédant une singularité isolée au point z0, peut s'écrire comme la somme d'une fonction harmonique

et d'une partie singulière

avec αn, βn ∈ C, γ ∈ R; les deux séries sont supposées convergentes, la première pour |z – z0| suffisamment petit, la seconde pour tout z ≠ z0. Alors h(z) = u(z) + s(z). Nous dirons que la singularité de h est non-essentielle si s(z) est de la forme

et newtonienne ou logarithmique si elle s'écrit

Our main object is to prove the following result.

THEOREM C. Let A be an affine translation plane of order qr ≧ q2 suchthatl∞, the line at infinity, coincides with the translation axis of A. Suppose G is a solvable autotopism group of A that leaves invariant a set Δ of q + 1 slopes and acts transitively on l∞ \ Δ.

Then the order of A is q2.

An autotopism group of any affine plane A is a collineation group G that fixes at least two of the affine lines of A; if in fact the fixed elements of G form a subplane of A we call G a planar group. When A in the theorem is a Hall plane [4, p. 187], or a generalized Hall plane ([13]), G can be chosen to be a planar group.

Recently the ℒ(q,λ) spaces have been investigated by many authors and the theory of these spaces has proved to be particularly important for research in partial differential equations (see for example [15], [16] and [18]).

The equations of elliptic type in these spaces were first studied by C. B. Morrey [8], [9], who applied his well-known imbedding theorems, and afterwards by S. Campanato [3], [4] with the aid of isomorphism theorems and the so-called fundamental inequalities due to him.

On the other hand, G. Stampacchia introduced the ℒ(q,λ) spaces of strong type [17], the structures of which are more general and complicated than those of ℒ(q,λ) Spaces in the usual sense, and greater part of them were characterized by him, L. C. Piccinini, Y. Furusho, the author and others (see [5], [11]-[14], [16] and [17]).

This paper is concerned with the structure of the derivation algebra Der L of the Lie algebra L with split Cartan subalgebra H. The Fitting decomposition

of Der L with respect to ad ad H leads to a decomposition

where

This decomposition is studied in detail in Section 2, where the centralizer of ad L∞ in D0(H) is shown to be

which is Hom(L/L2, Center L) when H is Abelian. When the root-spaces La (a nonzero) are one-dimensional, this leads to the decomposition of Der L as

where T is any maximal torus of D0(H).

A basic tool in the usual presentation of the Morita theorems is the correspondence theorem for projective modules. Let RM be a left R-module and B = HomR(M, M). When M is a progenerator, there is a close connection (in fact a lattice isomorphism) between left R-submodules of M and left ideals of B, which can be applied to the solution of problems such as characterizing when the endomorphism ring of a finitely generated projective faithful module is simple or right Noetherian. More generally, Faith proved that this connection can be retained in suitably modified form when M is just a generator in R-mod ([4], [2], [3]). In this form the correspondence theorem can be applied to show, e.g., that, when RM is a generator, then (a): RM is finite-dimensional if and only if B is a left finite-dimensional ring and in this case d(RM) = d(BB), and (b): If RM is nonsingular then B is a left nonsingular ring ([6]).

In [4] we showed that one can tell whether a submeasure on a Boolean algebra has a control measure or is pathological by comparing the Fréchet-Nikodym topology it generates to the universal measure topology of Graves. We then wondered if a submeasure could be decomposed into a part with a control measure and a part which is pathological or zero. This led to the problem of finding a Lebesgue decomposition for a submeasure on an algebra of sets with respect to a Fréchet-Nikodym topology.

In [6] Drewnowski proved a Lebesgue decomposition theorem for exhaustive submeasures with respect to “additivities” and a similar theorem for exhaustive Fréchet-Nikodym topologies. He asked if an exhaustive Fréchet-Nikodym topology could be decomposed with respect to another Fréchet-Nikodym topology. In [12] Traynor showed that the answer is “yes”.

Let G be a group and φ an automorphism of G. We say that φ is a pseudo-identity (pi) if, for each x ∈ G, there exists a finitely generated (fg) subgroup K = Kx(φ) of G such that x ∈ K and φ|K is an automorphism of K. It has been shown [1, 3] that such special automorphisms of abelian or nilpotent groups play an important role in homotopy theory; and it was indicated in [2] that their purely algebraic properties might well repay study.

The following facts about pi's are elementary.

PROPOSITION 0.1. Let φ be an automorphism of G and let n be a non-zerointeger. Then φ is pi if and only if φn is pi.

PROPOSITION 0.2. Let φ be a pseudo-identity of G and a an automorphismof G. Then αφα-1 is a pseudo-identity.

Soit ℰn l'anneau des germes en 0 des fonctions numériques de classe C∞ dans Rn. On écrira aussi ℰx pour ℰn où x est la variable dans Rn. Désignons par Diff (n) le groupe des germes en 0 des difféomorphismes locaux τ de classe C∞ d'un voisinage de 0 dans Rn sur un voisinage de 0 tels que τ(0) = 0. Soient G un sous-groupe de Lie de Glp(R) et C∞0(Rn, G) l'ensemble des germes en 0 des applications de classe C∞ de Rn dans G.

Regularity and complete regularity are important topological properties and several generalizations of them occur in the literature on separation axioms. The properties of certain of these variants of (complete) regularity are similar to those of (complete) regularity and their theories run, either in part or in the whole, parallel to the theory of (complete) regularity. All the more, analogies inherent in their definitions as well as the nature of results obtained in the process of their study suggest the need of formulating a coherent unified theory encompassing the theory of (complete) regularity and its generalizations. An attempt leading towards the fulfillment of this need constitutes the theme of the present paper.

Section 2 is devoted to preliminaries and basic definitions. In Section 3 we devise a framework which leads to the formulation of a unified theorv of (complete) regularity, almost (complete) regularity, ([26,], [27], [28]), (complete) s-regularity [13], (functionally) Hausdorff spaces, R1-spaces [3], and others.

The results in this paper respond to two rather natural questions about a polar decomposition A = UP, where U is a unitary matrix and P is positive semidefinite. Let λ1, …, λn be the eigenvalues of A. The questions are:

• (A) When will |λ1|, …, |λn| be the eigenvalues of P?

• (B) When will λ1/|λ1|, …, λn/|λn| be the eigenvalues of U?

The complete answer to (A) is “if and only if U and P commute.” In an important special case the answer to (B) is “if and only if U2 and P commute.“

Since these matters are best couched in terms of two different inertias, we begin with a unifying definition of inertia which views all inertias from a single perspective.

For each square complex matrix A and each complex number z let m(A, z) denote the multiplicity of z as a root of the characteristic polynomial

The aim of this note is to study the class group of a central Ω-Krull ring and to determine in some cases whether a twisted (semi) group ring is a central Ω-Krull ring. In [8] we defined an Ω-Krull ring as a generalization of a commutative Krull domain. In the commutative theory, the class group plays an important role. In the second and third section, we generalize some results to the noncommutative case, in particular the relation between the class group of a central Ω-Krull ring and the class group of a localization. Some results are obtained in case the ring is graded. Theorem 3.2 establishes the relation between the class group and the graded class group. In particular, in the P.I. case we obtain that the class group is equal to the graded class group. As a consequence of a result on direct limits of Ω-Krull rings, we are able to derive a necessary and sufficient condition in order that a polynomial ring R[(Xi)i∊I] (I may be infinite) is a central Ω-Krull ring.

Given vectors and (or functions f(x) and g(x)) we define the Hölder Quotient Hpq by

1

or in case of functions by

2

Here ‖·‖p and ‖·‖q are the usual Lp and Lq norms. We assume throughout that

If p and q are both greater than one then they are positive but if we allow p and q to be less than one then one of them must be positive and the other one must be negative. This may cause a problem if for example, some value ai is zero and p is negative. In this case we use the convention that and

On étudie, dans ce travail, l'hamiltonien − ½ Δ + V suivant deux points de vue distincts. Le premier, dans le paragraphe 1, consiste à faire une hypothèse de nature asymptotique sur le potentiel V : on suppose qu'en dehors d'une boule B, il est à croissance au plus polynômiale. On étudie la fonction de Green de H dans le complémentaire de la boule B précédente. La méthode consiste à utiliser le processus de générateur ½V stoppé sur le bord de B avec V jouant un rôle de création ou d'annihilation. On projette par une fonction d'exhaustion et on utilise un théorème de comparaison. C'est par un calcul élémentaire sur une équation du second ordre que l'on calcule les poids des espaces entre lesquels opère la fonction de Green du complémentaire de B définie par H.

The main result of this paper is the following regularity result:

THEOREM. Let D ⊂ CNbe a bounded, strongly pseudoconvex domain with bD of class Ck, k ≧ 3. Let Σ ⊂ bD be an N-dimensional totally real submanifold, and let f ∊ A(D) satisfy |f| = 1 on Σ, |f| < 1 on. If Σ is of class Cr, 3 ≦ r < k, then the restriction fΣ = f|Σ of f to Σ is of class Cr − 0, and if Σ is of class Ck, then fΣ is of class Ck − 1.

Here, of course, A(D) denotes the usual space of functions continuous on , holomorphic on D, and we shall denote by Ak(D), k = 1, 2, …, the space of functions holomorphic on D whose derivatives or order k lie in A(D).

A module M is called a serial module if the family of its submodules is linearly ordered under inclusion. A ring R is said to be serial if RR as well as RR are finite direct sums of serial modules. Nakayama [8] started the study of artinian serial rings, and he called them generalized uniserial rings. Murase [5, 6, 7] proved a number of structure theorems on generalized uniserial rings, and he described most of them in terms of quasi-matrix rings over division rings. Warfield [12] studied serial both sided noetherian rings, and showed that any such indecomposable ring is either artinian or prime. He further showed that a both sided noetherian prime serial ring is an (R:J)-block upper triangular matrix ring, where R is a discrete valuation ring with Jacobson radical J. In this paper we determine the structure of serial right noetherian rings (Theorem 2.11).

Dans [3], Peter Hilton a introduit la notion de “localisation relative” d'une extension de groupes à noyau nilpotent. Etant donné une extension de groupes

oú N est nilpotent, il s'agit de l'introduire dans un diagramme commutatif:

oú NP est la P-localisation de N.

L'idée (issue de la Topologie algébrique) est de tourner autant que possible l'absence de localisation maniable dans la catégorie des groupes. J'ai moi-même exploité cette idée dans [6], dans le cas oú une action de groupe est exercée sur G.

We correct some errors in [1] and extend some of the results there. Generally, we shall follow the terminology and notation of [1]. There is an error in the proof of Lemma 3.13 there, and consequently the subsequent results which depend on it are incorrect as stated. However, they are correct if we replace the condition “a-admissible” by “strongly a-admissible” (see [3] where this notion was introduced). We also show that the results in [1] are correct if the semilattices are assumed to be modular.

We shall change the terminology in [3] slightly.

Definition 1 (see [3]). Let A be a Boolean algebra and let D be a meet semilattice with 1. An admissible map f.A X D → D is called strongly admissible if

where a’ is the complement of a in A.

The hypercenter theorem [6] asserts that in a ring with no non-zero nil ideals an element commuting with a suitable power of each element of the ring must be central. In this paper we shall be concerned with a similar problem in the setting of rings with involution. Let R be a ring with involution *, let Z denote the center of R and let S = {x ∈ R|x = x*} be the set of symmetric elements in R. We define the symmetric hypercenter of R to be

What can one hope to say about H? That H need not equal Z is clear. For instance, in the ring R = F2 of 2 X 2 matrices over a field, if * is the symplectic involution, all symmetric elements are central, hence H = R but Z ≠ R. Furthermore if R is a noncommutative ring in which every symmetric element is nilpotent then even in this case H = R and Z ≠ R follows.

In the early days of quantum mechanics, Weyl asked the following question. Let λ be a non-zero real number, ℋa separable Hilbert space. Given certain (unbounded) operators W1,…,Wn,W1+, …, Wn+ on ℋ satisfying

(on a dense subspace D of ℋ) with all other commutators vanishing. Given also a function where ζ ∈ Cn. Let W = (W1 …, Wn) W+ = (W1+ …, Wn+). How does one associate to f an operator f(W, W+)? (Actually, Weyl phrased the question in terms of p = Re ζ, q = Im ζ, P = Re W, Q = Im W+ which represent momentum and position. In this paper, however, we wish to exploit the unitary group on Cn and so prefer complex notation.)

Let A = (Aij)l≦ij≦l be a Cartan matrix, i.e., Aii = 2 for all i and Aij is an integer ≦ 0 for i ≠ j, with Aij = 0 if Aji = 0. The size l of A is called its rank, for Lie-theoretic reasons, and may be larger than its matrix rank. We associate to A its Dynkin diagram, with vertices 1, 2, … , l, with AijAji lines joining i to j, and with an arrow pointing from i to j if Aij/Aji < 1, i.e., pointing toward the shorter root (see below). The Cartan matrix A is indecomposable if its diagram is connected, and symmetrizable if there exist positive rational numbers q1 … , ql with

qiAij = qjAji for all i and j.

Symmetrizability is automatic if the diagram contains no cycle.